Hydraulic swage presses are machines that with an array of suitable tooling called “dies” are able to reduce by pressing a product from one diameter to a smaller diameter in a cold state. The product pressed may typically be made of a metal such as steel and may be of cylindrical form but this is not necessarily the case. In the fluid power connector sector, the previously described “product” is called a ferrule and is used to connect a hose to a hose end fitting. Ferrule type connectors are of course also used in other industries, however, increasing demands in the fluid power sector, such as increasing pressure and longer endurance levels, mean that ferrules in that industry are required to do more work and, as a result, higher performance of the swage press is continually sought.
One conventional form of hydraulic swage press design can generally be described as the “cone” type. This type of swage press utilises a piston driven by hydraulic pressure with the piston having a forward operational face recessed in a frusto-conical configuration. This operational face is adapted to co-operate with a series of shoes, each carrying an inwardly facing die, with the shoes having an outer part frusto-conical surface co-operable with the operational face of the piston. In use, as the piston moves forward under applied hydraulic pressure, forward movement of the shoes is prevented and as a result the shoes and connected dies must move inwardly to provide a swaging movement. Many variations of this basic cone type design are possible including twin cone arrangements. Further, it is known to provide one or more pins extending in a circumferential direction between each adjacent die, the pin or pins being slidable within bores in the dies. Springs may also be provided in cone type swage presses extending in a circumferential direction acting between adjacent dies. The springs and pins provide location and stabilizing means for the dies and assistance for returning to an open condition but can fail when subjected to unusual forces during a swaging operation. The advantages of this design include ease of manufacture and therefore low cost, compactness, and a mechanical gain where the thrust exerted by the piston onto the dies can be as much as 4:1 due to the cone angle of the piston. Some disadvantages of the cone design include the “depth” of the assembly and the strain in the configuration due to mis-matching curvature of the frusto-conical surface in the piston and the part frusto-conical surfaces on the co-operating die shoes. This mis-matching of curvatures causes contact bearing to actually occur only along a line where the curves actually match which means, under load, that the conical surfaces actually distort and there is a significant impingement to varying degrees depending on load and relative piston position. As the actual measurement of the final swage diameter is made at the piston, accuracy suffers as well. The bearing load at this point is extreme and many machines of this type seize under load without significant amounts of lubrication.
To overcome some of the shortcomings of the cone type design, another form of swage press has been developed which may be described as a “scissor” type. This type of swaging press utilises a piston driven by hydraulic pressure having a forward V-shaped recess with flat bearing surfaces that, under pressure, moves toward a reaction block also having a V-shaped recess with flat bearing surfaces. Die carrying shoes are located between the piston and the reaction block having flat bearing surfaces engaging with either the bearing surfaces of the piston or the reaction block. The shoes (except those located in the corners of the V-shaped recesses) slide along the bearing surfaces as the piston moves toward the reaction block during a swaging operation. The die carrying shoes are maintained spaced from one another by spring members located between the shoes. The advantages of the scissor type design are that its dimension from front to rear is small compared to a similar dimension of the cone type. In addition, the scissor type design has high loading capability due to the full surface bearing contact described above. A significant disadvantage is, however, that it has a high manufacturing cost due mainly to the 1:1 mechanical gain (i.e. 1 mm of piston movement=1 mm change in swaging diameter) whereas the cone type may have as much as 4:1 mechanical gain. As a result, the piston in a scissor type press will be much larger than in the cone type press.
A further variation of the cone type swaging press may involve machining the frusto-conical surface of the piston in an octagonal shape, in the case of an eight die press, with eight essentially flat but inclined bearing surfaces, each co-operating with a flat but inclined bearing surface on the die shoe. The polygonal configuration would vary from an octagonal configuration depending on the number of dies used in the press. This type of swage press requires guide members to be located between the shoes with spring members also acting between the shoes similar to the spring members in the scissor type design. This arrangement has the advantage that it has a full contact bearing surface engagement similar to the scissor type machine but also has a mechanical gain advantage similar to a cone type design. The disadvantages of this design include that it is difficult to manufacture and the configuration, under radial load, results in the shoes tending to slide to the corners of the octagonal cone as this represents the outer most reactive low energy position. This means that the shoe guides mentioned above must be inserted between the shoes to keep them in correct position. Any wear in the guides will create an irregular swaging action.
In general, as the performance requirements of swage press equipment has increased, manufacturers are tending to produce scissor type designs or cone type designs but of larger diameter where the curvature of the cones are less mis-matched.
As the requirements of swage machines have increased with higher swaging loads, so has their flexibility. In earlier days, the swaging diameter was controlled by manufacturing different die sets of varying diameter with the piston moving to one fixed position (the end of stroke). In this position maximum bearing area is achieved with matching cone curvature. Many of these machines cost more in die tooling than in the actual cost of the swage press itself. More contemporary machines control the forward motion of the piston and hence are able to achieve a wide variation of finished swage diameters with a minimal amount of die tooling.
When manufacturing couplings for large diameter industrial hoses, it is more economical to use hollow annular stock that has been rolled and welded to produce a tubular structure. This, however, results in a product that has an axial weld bead where the wall section of the bead region is thicker and the structure/ductility of the metal varies significantly from the remainder of the material of the tubular structure. This can provide significant difficulties with swaging such a manufactured ring in conventional cone and other types of swaging presses and commonly requires positioning of the weld bead in a specific location for the swaging operation to be possible.